It is appreciated that it is very awkward and potentially hazardous for the average person to wire or rewire electrical connections involving electrical fixtures, such as lamps, outlet plugs and the like. Normally, this sort of work is left to the skilled tradesman; however, there are many householders who for various reasons wish to make their own installations. It would therefore be expedient for both the skilled tradesman and the householder to have a simple hazard-free form of installing lamp fixtures and the like on wall and ceiling outlet boxes. This problem has been appreciated for some time and as a result many solutions have been posed as exemplified in the following patents.
A simple form of plug-in arrangement is disclosed in U.S. Pat. Nos. 1,486,896; 1,511,594 and 2,671,821. The wall or ceiling outlet box has provided in a sealed face thereof a standard type of plug outlet. The lamp to be secured to the outlet box has a base plate which is coupled in one form or another to the outlet box. Before such coupling is completed, the lamp fixture plug is simply plugged into the outlet plug of the electrical box. This type of arrangement reduces hazard in the average householder making connections and for the skilled workman provides an expedient form of connection. It is appreciated, of course, that the outlet box has to have been prewired by a competent individual.
All of the devices described in the aforementioned patents significantly protrude into the electrical outlet box (or wall or ceiling if there is no such box). This degree of protrusion into the electrical outlet box is in contravention of most electrical safety codes. Furthermore, all of the devices described in the prior art patents require two or more steps for detachment or mounting of a fixture within appropriate connector.
In addition, the prior art devices cannot be used universally for connecting a wide variety of fixtures. For example, the devices of U.S. Pat. Nos. 1,486,896 and 1,511,594 are designed specifically for wall mounting wherein the downward weight of the fixture is required to maintain the connection. U.S. Pat. No. 2,671,821 discloses a hanger system limited to hanging type fixtures.
Canadian patent No. 1,040,606 discloses an electrical coupling system which simultaneously provides for electrical contact of the fixture to the outlet box wiring, while securing the light fixture in place. The electrical outlet box is provided with a face plate which presents the electrical contacts in combination with lug portions. The light fixture includes mating lug portions which on rotation clip into and secure the light fixture in place on the face plate. The lug portions on the light fixture also include electrical contacts which lead to the lamp of the fixture. Hence when the lug portions are engaged to support the light fixture, the electrical contacts engage to complete the circuit. The drawback with this system is that, due to the inter-relationship of the lugs and the electrical contacts, there is a limitation on the amount of support that can be provided in the lug systems while continuing to provide suitable engagement of the electrical contacts. Furthermore, the electrical contacts are left exposed thereby presenting potential hazard in mounting the light fixture in place or allowing the user to reach up into the outlet of the face portion and contact one or more of the live electrical leads.
Canadian patent No. 1,040,606 also suffers from the disadvantage of the prior art U.S. patents in that it cannot be universally applied to connecting a wide variety of fixtures. For example, FIGS. 1 and 2 of the prior art Canadian patent illustrate that a central threaded tubular rod is mounted to the coupling as a central tubular rod connector. The threaded tubular rod is relatively short and is designed to hold the cover plate in position and to provide a thread to attach a ring (or hook) upon which a light fixture or chain is hung. The disclosure describes use of the ring (or hook) in terms which are specific to the application of hanging a light fixture or chain therefrom.
In summary, prior art coupling devices suffer from the disadvantages that they protrude significantly into the electrical junction box; they are of complex design; and installation of the fixtures is typically complex (i.e. requiring two or more steps).